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// Copyright 2013 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#if V8_TARGET_ARCH_ARM64
#include "arm64/utils-arm64.h"
namespace v8 {
namespace internal {
#define __ assm->
int CountLeadingZeros(uint64_t value, int width) {
// TODO(jbramley): Optimize this for ARM64 hosts.
ASSERT((width == 32) || (width == 64));
int count = 0;
uint64_t bit_test = 1UL << (width - 1);
while ((count < width) && ((bit_test & value) == 0)) {
count++;
bit_test >>= 1;
}
return count;
}
int CountLeadingSignBits(int64_t value, int width) {
// TODO(jbramley): Optimize this for ARM64 hosts.
ASSERT((width == 32) || (width == 64));
if (value >= 0) {
return CountLeadingZeros(value, width) - 1;
} else {
return CountLeadingZeros(~value, width) - 1;
}
}
int CountTrailingZeros(uint64_t value, int width) {
// TODO(jbramley): Optimize this for ARM64 hosts.
ASSERT((width == 32) || (width == 64));
int count = 0;
while ((count < width) && (((value >> count) & 1) == 0)) {
count++;
}
return count;
}
int CountSetBits(uint64_t value, int width) {
// TODO(jbramley): Would it be useful to allow other widths? The
// implementation already supports them.
ASSERT((width == 32) || (width == 64));
// Mask out unused bits to ensure that they are not counted.
value &= (0xffffffffffffffffUL >> (64-width));
// Add up the set bits.
// The algorithm works by adding pairs of bit fields together iteratively,
// where the size of each bit field doubles each time.
// An example for an 8-bit value:
// Bits: h g f e d c b a
// \ | \ | \ | \ |
// value = h+g f+e d+c b+a
// \ | \ |
// value = h+g+f+e d+c+b+a
// \ |
// value = h+g+f+e+d+c+b+a
value = ((value >> 1) & 0x5555555555555555) + (value & 0x5555555555555555);
value = ((value >> 2) & 0x3333333333333333) + (value & 0x3333333333333333);
value = ((value >> 4) & 0x0f0f0f0f0f0f0f0f) + (value & 0x0f0f0f0f0f0f0f0f);
value = ((value >> 8) & 0x00ff00ff00ff00ff) + (value & 0x00ff00ff00ff00ff);
value = ((value >> 16) & 0x0000ffff0000ffff) + (value & 0x0000ffff0000ffff);
value = ((value >> 32) & 0x00000000ffffffff) + (value & 0x00000000ffffffff);
return value;
}
int MaskToBit(uint64_t mask) {
ASSERT(CountSetBits(mask, 64) == 1);
return CountTrailingZeros(mask, 64);
}
} } // namespace v8::internal
#endif // V8_TARGET_ARCH_ARM64
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